<!-- 切换主题色  -->
<template>
    <div>    
        <el-color-picker  @change="colorChange" v-model="colors.primary" ></el-color-picker>
    </div>
</template>
<script>
import generateColors from "../../utils/color";
import objectAssign from "object-assign";
export default {
    name: "App",
    data() {
        return {
            originalStylesheetCount: -1,//记录当前已引入style数量
            originalStyle: "",//获取拿到的.css的字符串
            colors: {
                //颜色选择器默认颜色值,这个值要和element-variables一样
                // primary: "sandybrown"
            },
            // primaryColor: "", //提交成功后设置默认颜色
            cssUrl: [
                "//unpkg.com/element-ui/lib/theme-chalk/index.css",
                "./static/css/index.css"
            ]
        };
    },
    methods: {
        colorChange(e) {
            if(!e)return;
            localStorage.setItem('color',e)
            this.primaryColor = this.colors.primary;
            this.colors = objectAssign(
                {},
                this.colors,
                generateColors(this.colors.primary)
            );
            this.writeNewStyle();
        },
        writeNewStyle() {
            let cssText = this.originalStyle;
            Object.keys(this.colors).forEach(key => {
                cssText = cssText.replace(
                    new RegExp("(:|\\s+)" + key, "g"),
                    "$1" + this.colors[key]
                );
            });
            if (this.originalStylesheetCount === document.styleSheets.length) {
                // 如果之前没有插入就插入
                const style = document.createElement("style");
                style.innerText =
                    ".primaryColor{background-color:" + this.colors.primary + "}" + cssText;
                document.head.appendChild(style);
            } else {
                // 如果之前没有插入就修改
                document.head.lastChild.innerText =
                    ".primaryColor{background-color:" +
                    this.colors.primary +
                    "} " +
                    cssText;
            }
        },
        getIndexStyle(url) {
            let that = this;
            var request = new XMLHttpRequest();
            request.open("GET", url);
            request.onreadystatechange = function() {
                if (
                    request.readyState === 4 &&
                    (request.status == 200 || request.status == 304)
                ) {
                    // 调用本地的如果拿不到会得到html,html是不行的
                    if (request.response && !/DOCTYPE/gi.test(request.response)) {
                        that.originalStyle = that.getStyleTemplate(request.response);
                        that.writeNewStyle()
                    } else {
                        that.originalStyle = "";
                    }
                } else {
                    that.originalStyle = "";
                }
            };
            request.send(null);
        },
        getStyleTemplate(data) {
            const colorMap = {
                "#3a8ee6": "shade-1",
                "#409eff": "primary",
                "#53a8ff": "light-1",
                "#66b1ff": "light-2",
                "#79bbff": "light-3",
                "#8cc5ff": "light-4",
                "#a0cfff": "light-5",
                "#b3d8ff": "light-6",
                "#c6e2ff": "light-7",
                "#d9ecff": "light-8",
                "#ecf5ff": "light-9"
            };
            Object.keys(colorMap).forEach(key => {
                const value = colorMap[key];
                data = data.replace(new RegExp(key, "ig"), value);
            });
            return data;
        }
    },
    mounted() {
        // 默认从线上官方拉取最新css,2秒钟后做一个检查没有拉到就从本地在拉下
        let that = this;
        // 如果是记住用户的状态就需要，在主题切换的时候记录颜色值，在下次打开的时候从新赋值
        this.colors.primary = localStorage.getItem('color')||this.colors.primary//例如
        this.getIndexStyle(this.cssUrl[0]);
        setTimeout(function() {
            if (that.originalStyle) {
                return;
            } else {
                that.getIndexStyle(that.cssUrl[1]);
            }
        }, 2000);
        this.$nextTick(() => {
            // 获取页面一共引入了多少个style 文件
            this.originalStylesheetCount = document.styleSheets.length;
        });
    }
};
</script>
<style>
</style>